An Investigation of Stress Intensification Factors of Laterals Compared to Tees – Part 2

Abstract This paper is an extension of the work presented in Part 1 [1], which investigated whether the Stress Intensification Factors (SIFs) of the 90-degree branch connections (tees) can be used for corresponding 45-degree branch connections (laterals) based on Finite Element Analysis (FEA). Part 1 explored the D/T and d/D limits not covered by ASME B31J-2017 Note 7: d/D ≤ 0.6 with D/T ≥ 50, and d/D > 0.6 with D/T ≤ 100. Size on size (d/D=1) branch connections were not considered in Part 1. In this paper, branch connections with D/T and d/D ranges already covered by ASME B31J-2017 and B31J-2023 (D/T < 50, d/D ≤ 0.6) are investigated to verify and validate the method. Size on size branch connections (d/D = 1) are also included in the study. In addition, a method to calculate flexibility factors (k-factors) of branch connections using FEA is proposed. Flexibility factors of the tees calculated using FEA are verified by comparing them with ASME B31J-2017 values. Furthermore, flexibility factors calculated by FEA for 90-degree and 45-degree branch connections are compared for D/T ≤ 100 and d/D ≤ 1.0 because ASME B31J Note 7 (a) currently (as of B31J-2023) states that the flexibility factors are applicable only when the branch pipe axis is normal to within 5 degrees of the surface of the run pipe.